Variable oscillator for code practice (CB7317E)

This circuit is from Popular Electronics from the 90s. The integrated circuit is not very common nowadays.

Sound Reinforcer (CB12868E)
The original transistor for this circuit from a 1973 publication is germanium, but a silicon...
Variable Frequency Oscillator (CB4050E)
This VFO was found in a 1980s documentation. The central frequency is given by the crystal and the...
Differential temperature alarm (CB26159E)
The sensors in this circuit that triggers when the temperature goes out of a certain range are...